International Research Journal of Engineering and Technology (IRJET)
e-ISSN: 2395-0056
Volume: 08 Issue: 05 | May 2021
p-ISSN: 2395-0072
www.irjet.net
Transport Refrigeration Unit Control using CAN Communication Shreeyas Pravin S PG student, Department of Electrical and Electronics Engineering, RV college of Engineering, Karnataka, India
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Abstract – Transport Refrigeration units are used for
market today. However, selection of the right temperature sensor largely depends on the nature of application. Modern semiconductor temperature sensors (IC Based) offer high linearity and accuracy over an operating range of -55° C to 150° C. Thermistors have the best sensitivity among the sensors available but are the most non-linear. However, they are popularly used in portable applications such as battery management systems. Thermocouple have the widest operating range but would require cold junction compensation. Resistance Temperature Devices (RTD) are accurate with an operating range of -200° C to 850° C and are used in refrigeration applications [5]. As there are multiple temperature sensors present in a TRU and containers, communicating and prioritising individual sensor unit with the Electronic Control Unit (ECU) is one of the major challenges. However, the evolution of Controller Area Network (CAN) by Bosch in the 1980’s redefined the communication protocol in automobile industry [6]. CAN is a serial half duplex asynchronous communication-based protocol. It uses differential communication with CAN H and CAN L outputs to minimize the effect of external noise signal during communication. In the past, automotive manufacturers connected electronic devices using wires [7]-[8]. As the number of electronic components increased in the vehicles, it resulted in bulky wire harnesses that were heavy and expensive [9] – [10]. It accounted for multiple ECU’s in the system. From the development of CAN protocol the number of ECU’s came down to one and there are multiple CAN interfaces to communicate with the ECU.
maintaining the quality of food products and transporting them from one place to another. It can be observed that one of the most important parameters in TRU is temperature. There are multiple temperature sensors located physically at different places within the refrigeration systems and the containers to record the temperatures. Therefore, the harness required to connect these temperature sensors with the controller is high. A small temperature sensor module which produces CAN signals that can directly be connected to the receiver interface is proposed in this work. This will make the system compact as the amount of harness required is reduced and it also reduces the overall cost. The prototype was built considering PT(Platinum) temperature sensor. A signal conditioning circuit is designed to improve the resolution, accuracy and sensitivity. Simulation of signal conditioning circuit is performed in PSIM and the results were verified. Error analysis was performed using LTSPICE considering the tolerance values using Monte-Carlo method. The error offered by the circuit was found to be varying between 0.808℃ to 0.5739 ℃ for -50 to 150 ℃ respectively. It was also observed that the sensitivity is improved 11 times with the help of a signal conditioning circuit. The hardware module is built using ATMEGA 328P microcontroller and MCP 2515 CAN controller. The microcontroller is programmed using Embedded C language. Testing is carried out between the melting point of ice (0 ℃) to boiling point of water (100 ℃). Key Words: Transport Refrigeration unit, CAN Communication, Temperature Monitoring, Temperature Sensors, Signal Conditioning.
1.1 Block Diagram of the transmitter The block diagram of the transmitter unit is shown in Fig 1. The temperature sensor chosen is PT 100 / PT 1000 whose output is in resistance. The resistance is converted to proportional output voltage through a signal conditioning circuit. In addition, the signal conditioning circuit has been designed considering the scope for resolution improvement and better system performance. The output of the signal conditioning circuit is analog signal and hence needs to be converted to an equivalent digital value. It is done with the help of internal ADC of ATMEGA 328P microcontroller.
1.INTRODUCTION In the 1830’s the consumer demand for fresh food was growing. This led to the invention of refrigeration system by American inventor Jacob Perkins in the year 1834 [1]. Since then, there have been significant developments in modern refrigeration systems. Although, refrigeration system was primarily built for storing food products in the initial days, it also proved vital in pharmaceutical industry as the medicines had to be maintained at a specific temperature. One of the major concerns with the Refrigeration systems was its inability to transport food and medical products from one place to another. This paved the way for developing Transport Refrigeration Unit (TRU) in the year 1940 [2]-[4]. Ever since its emergence, the pattern of food consumption has totally changed. There are multiple temperature sensors mounted in the TRU at different places for temperature measurement. In addition, there are different types of temperature sensors available in the
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The microcontroller is interfaced with MCP 2515 CAN controller. The communication between MCP 2515 and ATMEGA 328P is through Serial peripheral interface (SPI). The inbuilt TJA1050 Transceiver is responsible for facilitating the communication between the CAN controller and ATMEGA 328P.
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